ASSIGNMENT OF THE 278-NM ELECTRONIC BAND SYSTEM OF BENZIMIDAZOLE [1,3-BENZODIAZOLE] AS PI-STAR-PI BY ROTATIONAL BAND CONTOUR ANALYSIS

The 000 band of the 278-nm electronic band system of benzimidazole has been rotationally analyzed by computer simulation of its rotational contour. It has been shown to be an A B hybrid with an intensity ratio B A = 0.11. The S1-S0 electronic system is assigned as A ̃1A′(ππ*)- X ̃1A′. Since the same result has already been reached for other ring condensed aza-aromatic compounds, we conclude that the number and location of nitrogen atoms in these molecules do not change the nature of the S1-S0 transition. © 1991.